The Centers for Disease Control (CDC) has stated that COPD (chronic obstructive pulmonary disease) has escalated to the 3rd leading cause of death in this country. See, A M, Miniño, Xu J Q, and Kochanek K D (2010), ‘Deaths: Preliminary Data for 2008.’, National Vital Statistics Reports, 59 (2), John Walsh (President, COPD Foundation) remarked that “It's unacceptable that COPD has gone from the fourth leading cause to the third twelve years sooner than what was originally projected. This wake-up call intensifies our declaration of war on COPD and points to the importance of improved awareness, prevention, detection and treatment to decrease the burden of COPD”. {Foundation, COPD (2010), ‘New CDC Report Puts COPD in #3 Spot in Mortality Rates’} In contrast to other top causes of death, COPD is the only disease in the top ten that has consistently increased in frequency over the past 4 decades. Consequently COPD represents one of the largest uncontrolled disease epidemics in the U.S.; it currently includes 15-20 million diagnosed cases with perhaps a similar number undiagnosed. In the U.S., there are approximately 90 million current or former smokers, (Association, 2008); thus, a huge population is at risk of developing COPD. COPD is defined by the Global Initiative for Chronic Obstructive Lung Disease (GOLD) as a disease state characterized by airflow limitation that is not fully reversible. Heron et al., “Deaths: Final Data for 2006.” National Vital Statistics Reports 57(14): 1-135 (2009).
There is clear recognition that COPD includes both emphysema and small airway disease; however, there is little appreciation of how to identify COPD early—before there is significant airflow obstruction and clinical impairment. In addition, evidence from the COPD Gene study suggests that COPD is likely several diseases but currently the only tool that seems to provide any clinical differentiation of the genotypes is “gas trapping” patterns assessed by HRCT (High Resolution X-ray Computed Tomography).
Current approaches for the evaluation of pulmonary lung function use global measures of pulmonary function such as spirometry (e.g., forced expiratory volume in 1 second (“FEV1”)) and whole body plethysmography. While spirometry is low cost and widely available, it does not yield any regional information about ventilation distribution or ventilation dynamics in the lung.
Currently available lung imaging methods include x-ray CT, which offers anatomic detail but limited functional information, and nuclear techniques such as scintigraphy, which provide regional information at low resolution in two dimensions rather than three (or more). Also, these modalities deliver ionizing radiation, which limits their repeat use in patients, especially in clinical trials.
More recently, hyperpolarized gas MRI using the stable isotopes 3He and 129Xe has offered hope for non-invasive, regional assessment of lung function. Unfortunately, this technology is relatively expensive and has not been widely disseminated.